Changing email address on Subject line to displaying the customer's Last Name instead?

The following information is required to get an answer:
Get this information from the PHP diagnostic (in the configuration wizard).
Gallery URL (optional but very useful): http://thefamilytreee.ca/Gallery3/
Gallery version: v1.5-RC2
Apache version: Sorry, not sure of this one
PHP version (don't just say PHP 4, please): I believe it is PHP 5.0
Graphics Toolkit: Front Page plus Adobe Photoshop/DreamWeaver
Operating system: Windows
Web browser/version (if applicable): Firefox 1.0.7

This version of Gallery (v1.5-RC) is working together with Gallery Cart and uses a customized version of it by NotGoddess. I've tried to get in touch with Sara but it is as if she has fallen off the face of the earth.

My client wants to customize it further and would like his own customer's last name to appear on the subject line of the email he receives when an order is made.

I no longer remember how to make this sort of change and came here hoping someone would be able to guide me to make this change.

Thank you for any help received.

Magician

Hi, Jens....Ya, I realize Gallery 1.5-RC2 is an old one but it is also a good one!

Can you suggest any Galleries which will work with Gallery Cart? Or even one which will work as well as it?

It is getting harder and harder to make requested changes for my client as I am not familiar with PHP. I've printed out over 100 pages making up Gallery Cart to figure out how to make the change I was mentioning. I figure it is located somewhere within the configuration file?

I am looking forward to your suggestions!

Thanks.

Magic